A 20-year-old female presents with pelvic and back pain severe enough to miss work beginning with the onset of menses. Physical examination supports the diagnosis of primary dysmenorrhea. The most likely cause of her condition is:

The female reproductive system can have many problems, including: Menstrual cycle: A normal menstrual cycle lasts 28 days, but can range from 21 to 42 days. Pain: Pain in the lower abdomen, upper thighs, or back. Bleeding: Bleeding may be heavier or lighter than usual, or it may last longer than your usual period. Infections: Such as a yeast infection, or sexually transmitted infections (STIs) like chlamydia or gonorrhea. Rashes, sores, blisters, or lumps: In the vagina or on the vulva. Fertility issues: Such as polycystic ovary syndrome (PCOS), primary ovarian insufficiency (POI), or... Show more

The female reproductive system can have many problems, including:
Menstrual cycle: A normal menstrual cycle lasts 28 days, but can range from 21 to 42 days.
Pain: Pain in the lower abdomen, upper thighs, or back.
Bleeding: Bleeding may be heavier or lighter than usual, or it may last longer than your usual period.
Infections: Such as a yeast infection, or sexually transmitted infections (STIs) like chlamydia or gonorrhea.
Rashes, sores, blisters, or lumps: In the vagina or on the vulva.
Fertility issues: Such as polycystic ovary syndrome (PCOS), primary ovarian insufficiency (POI), or cancer of the uterus, cervix, or ovaries.
Other conditions: Such as endometriosis, uterine fibroids, gynecologic cancer, HIV/AIDS, interstitial cystitis, cervical cancer, breast cancer, urinary infections, and uterine prolapse. 

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